It is known to those skilled in the art that ethers, including both symmetrical and unsymmetrical ethers, may be prepared by reacting an alcohol with another alcohol to form the desired product. The reaction mixture, containing catalyst and/or condensing agent may be separated and further treated to permit attainment of the desired product. Such further treatment commonly includes one or more distillation operations.
Hydrogenation catalysts are known and are generally selected from Group VIII of the Periodic Table. Suitable metals include, but are not limited to, platinum, palladium, tin, nickel and copper alone, or in combination.
In U.S. Pat. No. 3,955,939 to Sommer et al. (1976), there is disclosed the production of a water-free mixture of isopropyl alcohol, diisopropyl alcohol, diisopropyl ether and by-products by the catalytic hydration of propylene in the gaseous phase at temperatures of 140.degree.-170.degree. C., wherein the water-free mixture formed according to the process can be used directly as an additive to gasoline fuel.
Conversion of acetone to MIBK is addressed in U.S. Pat. No. 3,953,517. The catalyst is a noble metal. In U.S. Pat. No. 5,059,724 a method is disclosed for the selective production of methyl isobutyl ketone.
In U.S. Pat. No. 5,017,729 there is disclosed a multistage process for producing phenol, wherein acetone is hydrogenated in the fourth step.
The use of zeolites for certain reactions is known in the art. .beta.-zeolite was first synthesized at Mobil R&D labs and exhibited improved thermal and acid stability over previously synthesized zeolites.
One of the earliest disclosures of zeolite beta was in U.S. Pat. No. 3,308,069 (1967) to Wadinger et al.
J. B. Higgins, et al. of Mobil Research and Development published an article in Zeolites, 1988, Vol. 8, November, 446-452 titled "The Framework Topology of Zeolite Beta." In the article Higgins et al. disclose what is known about the framework topology of zeolite beta. The information has been determined using a combination of model building, distance-least-square refinement and powder pattern simulation.
In an article titled "Cumene Disproportionation over Zeolite .beta. I. Comparison of Catalytic Performances and Reaction Mechanisms of Zeolites," Applied Catalysis, 77 (1991) 199-207, Tseng-Chang Tsai, Chin-Lan Ay and Ikai Wang disclose a study demonstrating that cumene disproportionation can be applied as a probe reaction for zeolite structure. It is revealed that zeolite beta would have application potential in the production of diisopropylbenzene for reasons of activity, selectivity and stability.
In a second part of the article, "II. Stability Enhancement with Silica Deposition and Steam Pretreatment", Ibid, pp. 209-222, Tsai and Wang disclose their development of two methods to improve the stability of zeolite beta, silica deposition and steam pretreatment.
Patents in the art which employ zeolite beta relate mainly to dewaxing, and cracking of hydrocarbon feedstock.
An article titled "Beta Zeolite as Catalyst or Catalyst Additive for the Production of Olefins During Cracking or Gas Oil," was written by L. Bonetto et al., 9th International Zeolite Conference, July 1992, FP 22. The authors note that with the greater demand for oxygenated compounds there is indication there might be increased demands for catalysts and conditions which maximize C.sub.3, C.sub.4 and C.sub.5 olefins. They suggest that .beta.-zeolite could be used alone or combined with Y-zeolite as a suitable zeolite component. Various catalysts were studied with respect to minimization of diffusional requirements and zeolite stability.
U.S. Pat. No. 4,419,220, to Mobil, discloses a process for dewaxing a hydrocarbon feedstock containing straight chain paraffins which comprises contacting the feedstock with a .beta.-zeolite beta catalyst having a Si:Al ratio of at least 30:1 and a hydrogenation component under isomerization conditions.
Another European Application to Mobil, EP 0 094 827, discloses simultaneous catalytic hydrocracking and hydrodewaxing of hydrocarbon oils with .beta.-zeolite.
In European Patent Application 0 095 303, to Mobil, there is a disclosure of dewaxing distillate fuel oils by the use of .beta.-zeolite catalysts which, preferably have a silica:alumina ratio over 100:1. Ratios as high as 250:1 and 500:1 are disclosed as useful.
Another U.S. Pat. No. 4,518,485, to Mobil, discloses a process for dewaxing a hydrocarbon feedstock containing paraffins selected from the group of normal paraffins and slightly branched paraffins and sulfur and nitrogen compounds where, after conventionally hydrotreating the feedstock to remove sulfur and nitrogen, the hydrotreated feedstock is dewaxed by contacting the feedstock with a catalyst comprising a .beta.-zeolite having a silica/alumina ratio of at least 30:1.
In U.S. Pat. No. 4,740,292, to Mobil, there is disclosed a catalytic cracking process which comprises cracking a hydrocarbon feed in the absence of added hydrogen with a cracking catalyst comprising a .beta.-zeolite component and a faujasite component comprising at least one crystalline aluminosilicate of the faujasite structure, the weight ratio of the faujasite component to the .beta.-zeolite component being from 1:25 to 20:1.
Large pore .beta.-zeolite has been employed in the synthesis of industrially important para-cumene by toluene isopropylation. See "Toluene Isopropylation over Zeolite .beta. and Metallosilicates of MFI Structure," P. A. Parikh et al., Applied Catalysis, A, 1992, 90, p. 1.
In European Patent 323138 and U.S. Pat. No. 4,906,787, there is disclosed a catalytic process for converting light olefins to ethers suitable as high octane blending stocks carried out by contacting the olefin, especially propene, with water and alcohol recovered from a downstream distillation operation in an olefin conversion unit in the presence of an acidic zeolite catalyst. In this work diisopropyl ether (DIPE) was prepared from C.sub.3 H.sub.6 and aqueous iso-PrOH in the presence of silica-bound zeolite Beta catalyst at 166.degree..
In another European Patent, EP 323268, light olefins are converted to alcohols and/or ethers in the presence of .beta.-zeolite.
In U.S. Pat. No. 5,144,086, to Harandi et al., there is disclosed an integrated multistage process for the production of diisopropyl ether and substantially pure propene wherein in the second stage isopropanol containing about 0%-20% water is contacted with an acidic large pore zeolite etherification catalyst which comprises a .beta.-zeolite having a Si:Al ratio of about 30:1 to 50:1.
Another group of molecular sieve zeolites which have been investigated for industrial application is pentasil zeolites. The pentasil family of zeolites contains a continuing series of which ZSM-5 and ZSM-11 are end members. See T. E. Whyte et al. "Zeolite Advances in the Chemical and Fuel Industries: A Technical Perspective," CATAL. REV.-SCI. ENG., 24, (4 ) , 567-598 (1982 ) .
A good overview of applications for zeolites, including pentasil type zeolites is found in an article titled, "Zeolite Catalysts Face Strong Industrial Future", European Chemical News, Jul. 10, 1989, p. 23. For example, medium pore H-ZSM-5 is sometimes added to a zeolite Y catalytic cracking catalyst to increase the aromatics content and hence motor octane, of the gasoline fraction. In the limited space of ZSM-5, where two pore systems of about 5-6.ANG. in diameter intersect to give spatial regions of around 9.ANG. diameter at the intersections, there is a cutoff around C.sub.10 to C.sub.11 for products from transformation of a wide range of feedstocks, including alkanes, olefins and alcohols.
The Pentasil ZSM-5 is a catalyst used for converting methanol to gasoline, processing C-8 streams, selectively isomerizing m-cresol to p-cresol, suppressing the formation of diphenylalanine in the production of aniline, and producing pyridine and .beta.-picoline from acetaldehyde, formaldehyde and ammonia.
In an Article titled "Shape Selective Reactions with Zeolite Catalysts", J. CATAL., 76, 418 (1982), L. B. Young et al. report data on selectivity in xylene isomerization, toluene-methanol alkylation, and toluene disproportionation over ZSM-5 zeolite catalysts. Some of the ZSM-5 zeolites in this study were modified. It was demonstrated that appropriately modified ZSM-5 class zeolites are capable of generating uniquely selective compositions. Intrinsic reactivities and selectivities are considerably altered with these modified catalysts.
There is a discussion of the shape selective properties of ZSM-5 in "A Novel Effect of Shape Selectivity: Molecular Traffic Control In Zeolite ZSM-5", by E. G. Derouane, et al., J. CATAL., 65, 486 (1980). Some of the observations included the following: (i) linear aliphatics diffuse rather freely in the ZSM-5 framework and can be adsorbed in both channel systems; (ii) isoaliphatic compounds experience stearic hinderance which may restrict their diffusion in the sinusoidal channel system; and (iii) aromatic compounds and methyl substituted aliphatics have a strong preference for diffusion and/or adsorption in the linear and elliptical channels.
E. G. Derouane et al. studied shape selective effects in the conversion of methanol to higher hydrocarbons and alkylation of p-xylene on pentasil-family zeolites. Some of these zeolites were modified by the incorporation of phosphorous, or embedded in a silica filler. Their findings are reported in "Molecular Shape Selectivity of ZSM-5, Modified ZSM-5 and ZSM-11 Type Zeolites", in FARADAY DISCUSSIONS, 72, 331 (1981).
P. Chu et al. report results of one study in "Preparation of Methyl tert-Butyl Ether (MTBE) over Zeolite Catalysts", IND. ENG. CHEM. RES., 26, 365 (1987). They reported that ZSM-5 and ZSM-11 have been identified to be highly selective zeolite catalysts for the preparation of MTBE from isobutylene.
Another reference which discusses the use of pentasil zeolites in MTBE service is by G. H. Hutchings, et al., CATAL. TODAY, 15, 23 (1992).
U.S. Pat. No. 4,058,576 to Chang et al. teaches the use of (pentasil-type) aluminosilicate zeolites, such as ZSM-5, having a pore size greater than 5 angstrom units and a silica-to-alumina ratio of at least 12, to convert lower alcohols to a mixture of ethers and olefins.
Japanese Patent 82-07432 teaches the use of zeolites, particularly mordenites and faujasites, to make dialkyl ethers containing primary or secondary alkyl groups by the liquid phase dehydration of alcohols.
In allowed U.S. patent application Ser. No. 07/917,218, there is disclosed a method for preparing methyl tertiary butyl ether by reacting butanol and methanol in the presence of a catalyst comprising a super-acid alumina or a faujasite-type zeolite.
In U.S. Pat. No. 5,081,318, a Y-type zeolite modified with fluorosulfonic acid is disclosed.
In U.S. Pat. No. 5,208,387, also to Harandi et al., there is disclosed a process for the acid catalyzed production of DIPE from propene and water feed stream that eliminates the propene recycle stream to the olefin hydration reactor and achieves high propene conversion. This process is carried out in two stages wherein the first stage comprises a zeolite catalyzed hydration and etherification of propene employing a minimum of water feed and the second stage converts unconverted propene from the first stage reactor by hydration and etherification to DIPE.
In an article titled "Race to License New MTBE and TAME Routes Heats Up", Rotman, D., Chemical Week, Jan. 6, 1993, p. 48, there is a review of new technology at several different companies which centers around skeletal isomerization, particularly of C.sub.4 and C.sub.5 olefins. The interest in this technology is fueled by the promise of dramatically increased and relatively inexpensive isobutylene and isoamylene that could boost MTBE and TAME production, often constrained by the amounts of available isobutylene in refinery or steam cracker streams. DIPE production from propylene is also discussed.
Mobil Corp. has disclosed new etherification technology that can produce fuel oxygenates based only on olefinic refinery streams and water. This process has the potential to allow refiners to produce oxygenates without having to rely on an external supply of alcohols. The technology is developed around diisopropyl ether (DIPE) based on propylene. The DIPE has similar physical and blending activities to MTBE and TAME and is a perfectly acceptable fuel oxygen source. Wood, A., Chemical Week, Apr. 15, 1992, p. 7.
None of the available references would seem to suggest the one-step conversion of low value crude acetone in a by-product stream into useful oxygenate products. The portion of said by-product stream which typically comprises acetone is about 20% to 80%. It would greatly enhance the economics of any process to produce MTBE or other oxygenates if acetone from a by-product stream could be converted in one step to useful oxygenate products which could be fractionated to isolate diisopropyl ether (DIPE) and isopropyl tertiary butyl ether (IPTBE).